Research progress of supported hydrodesulfurization catalyst

1.  Preparation

The preparation conditions (such as impregnation method, metal loading capacity, activation process, etc.) have certain influence on the structure, morphology and chemical state of HDS catalyst.

Hydrodesulfurization catalysts are usually prepared by impregnation methods, including equal volume impregnation method and excess impregnation method. Metal components can be bring in co-dipping or distributed dipping. For each metal component, it also includes one - time impregnation method and stage impregnation method.

In Co-Mo/Al2O3 prepared by co-impregnation and distribution impregnation, the Co phase obtained after sulfidation is basically the same. Many studies have shown that the dispersion and HDS activity of catalysts can be improved by adding chelator to the impregnation solution.In addition, the preparation of catalysts using thio-heteropoly-anionic organomeric complexes and metal clusters containing sulfur and active metals instead of inorganic salt impregnation , has gradually attracted the interest of researchers, because in the preparation of catalysts using the above compounds, the proportion of auxiliaries and the distribution of active components of catalysts can be more accurately controlled, so that the prepared catalysts rarely underwent structural restructuring during vulcanization.Theoretically, a relatively intact surface structure can be obtained to reduce the loss of auxiliary atoms to the carrier.

In the catalyst with Al2O3 as the carrier, the carrying capacity of Mo is generally between 8wt% and 15wt%, the amount of additives is generally selected empirically according to the carrying capacity of Mo usually around 1wt% to 5wt%. It is found that when the content of Mo is constant, co-Mo-S increases with the increase of Co content. When the Co/Mo ratio reaches a certain level and the Co loading continues to increase, the Co will mainly exist in the form of Co9S8, but the activity of the catalyst will be reduced.

Sulfidation is a very important step for HDS catalysts. In addition to converting the calcined oxidized catalyst into an active sulfurized catalyst, the sulfurization process also has a great influence on the structure of the catalyst. The sulfurization temperature is an important parameter of the sulfurization process. As the sulfidation temperature increases, the number of MoS2 edges decreases, In the region with higher Co content, Co will precipitate to form Co9S8.